package com.example.user.myfirstapp.common;

import java.security.MessageDigest;

/**
 * Created by user on 2016/5/23.
 */
public class StringHelper {

    /*
     * 加密
     * @param source     要加密的字符串
     * @return       加密后的字符串
    */
    public static String md5EncryptString(String source){
        char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
        try {
            byte[] btInput = source.getBytes();
            // 获得MD5摘要算法的 MessageDigest 对象
            MessageDigest mdInst = MessageDigest.getInstance("MD5");
            // 使用指定的字节更新摘要
            mdInst.update(btInput);
            // 获得密文
            byte[] md = mdInst.digest();
            // 把密文转换成十六进制的字符串形式
            int j = md.length;
            char str[] = new char[j * 2];
            int k = 0;
            for (int i = 0; i < j; i++) {
                byte byte0 = md[i];
                str[k++] = hexDigits[byte0 >>> 4 & 0xf];
                str[k++] = hexDigits[byte0 & 0xf];
            }
            return new String(str);
        } catch (Exception e) {
            return null;
        }
    }

    /// <summary>
    /// 截取字符串
    /// </summary>
    /// <param name="sourceStr">要截取的字符串</param>
    /// <param name="length">截取长度</param>
    /// <returns></returns>
    public static String cutString(String sourceStr, int length)
    {
        if (sourceStr.length() <= length)
            return sourceStr;
        else
            return sourceStr.substring(0, length) + "...";
    }
}
